Organic Light Emitting Diode (OLED) display has been a focus of research in display technology. As compared to liquid-crystal display (LCD) apparatuses, OLED display apparatuses have many advantages such as low power consumption, low fabrication cost, self-illumination, a wider viewing angle and faster response. As such, OLED displays have found a wide range of applications such as in mobile phones, personal digital assistance (PDAs), digital cameras, televisions, tablet computers, and laptop computers.